[core][a11y] Enable Escape key dismissal for Tooltips

[ggdouglas]

Fixes #7594

Summary

Adds Escape key support to dismiss Tooltips, bringing Blueprint into compliance with WCAG 2.1 Success Criterion 1.4.13 and the WAI-ARIA Tooltip Pattern.

Before	After

Problem

Tooltips in Blueprint could not be dismissed using the Escape key, which violates:

1. WCAG 2.1 SC 1.4.13 (Content on Hover or Focus) - requires a mechanism to dismiss content without moving pointer hover or keyboard focus
2. WAI-ARIA Tooltip Pattern - explicitly specifies that pressing Escape should dismiss tooltips

Previous Behavior

• Tooltip had canEscapeKeyClose={false} hardcoded
• Even if enabled, Escape wouldn't work because Overlay2's handler only fires when the container has focus
• Tooltips use autoFocus={false} to avoid stealing focus on hover

Solution

Added a document-level Escape key listener to Overlay2 that activates when autoFocus={false}. Tooltip no longer hardcodes canEscapeKeyClose={false}, allowing it to inherit the default true value from Overlay2 while keeping autoFocus={false} to prevent focus steal on hover.

Testing

1. Hover over a tooltip target
2. Tooltip appears
3. Press Escape key
4. Tooltip dismisses without moving pointer
5. Focus remains on the original element

[changelog-app]

Generate changelog in packages/core/changelog/@unreleased

Type (Select exactly one)

• Feature (Adding new functionality)
• Improvement (Improving existing functionality)
• Fix (Fixing an issue with existing functionality)
• Break (Creating a new major version by breaking public APIs)
• Deprecation (Removing functionality in a non-breaking way)
• Migration (Automatically moving data/functionality to a new system)

Description

[core][a11y] Enable Escape key dismissal for Tooltips

Check the box to generate changelog(s)

• Generate changelog entry

[svc-palantir-github]

Add functionality to allow Tooltips to be esc-key closed

Build artifact links for this commit: documentation | landing | table | demo

This is an automated comment from the deploy-preview CircleCI job.

[mm-wang]

Any chance we can get a test for multiple overlays?

[mm-wang]

question: Open to using React Testing Library for new tests?